Rotary drier, kiln, and the like



Jan. 19, 1954 BQJNER ROTARY DRIER, KILN, AND THE LIKE Filed Dec. 5, 1949 Patented Jan. 19, 1954 Application December 5, 1949, Serial No. 131,217

Claims priority, application Sweden October 6, 1949 Claims.

This invention relates to an improvement of rotary driers or kilns for drying or other heat treatment of granular, pulverulent or similar goods and consisting of a drum or cylinder the interior of which is divided by means of substantially radial partitions into longitudinal, substantially sector-shaped channels through which the goods to be treated and a heat delivering gas are conducted in the same direction or in countercurrent and in direct contact with each other. The drier or kiln may either be rotatable as a whole or the drum may be stationary while the partitions form a cage rotatable in the drum.

In rotary driers or kilns of said type the material to be dried or subjected to a heat treatment is continuously supplied at one end of the drum and catched by the partitions of the cage during the rotation and distributed on the different sector-shaped channels through which the material then gradually advances during the rotation. During this passage through the channels of the drum the material slides or rolls on the partitions and the inner surface of the drum mantle and ofifers in this manner constantly changing contact surfaces to the drying gas flowing through the channels.

In many cases difficulties arise in the operation of such driers on account of the tendency of the goods to adhere to the partitions and the inner surface of the drum, particularly at the feeding end where the material supplied has the highest content of moisture. The coatings thus formed reduce the drying effect in as much as they cause an irregular distribution and feeding of the material through the channels of the drum and reduce the transfer of heat to the goods by isolating the surfaces of the partitions and the inner mantle surface. Goods of this nature are for instance moist lime mud from the cellulose factories and slurry for the burning of cement in rotary cement kilns operating according to the wet process. a r

The chief object of my invention is to remove said drawback by an improved form of the cage of the drier or kiln whereby the goods supplied is caused to come into contact with one side only of the partitions while the heat delivering gases pass through the channels in contact with both sides of the partitions. In this manner the partitions will always be heated by the gases at least on the side not in contact with the material treated and the heat taken up from the gases by the partitions will be supplied by conduction to the material possibly adhering to the partitions so that such material is more rapidly dried and loosened from the partitions.

A further object of the invention is to facilitate the loosening of material adhering to the partitions or to the inner wall of the drum by the provision of a cage in the drum which during the operation of the drier can perform a rotary or rolling movement in relation to the drum in such manner that the cage constantly inpacts or bumps against the inner wall of the drum during the rotation, thus promoting the loosening of adhering material from the partitions as well as from the inner wall of the drum. This improvement is particularly valuable when the drum as well as the cage are rotatably journalled.

In the accompanying drawings I have shown two embodiments of my invention. Fig. 1 is a longitudinal central section of a rotary drier in which two different cages are arranged in series, the left one being according to the first embodiment of the invention. Fig. 1 is a section on the line l-I in Fig. 2. Fig. 2 is a cross-section on the line 2-2 in Fig. 1. Fig. 3 shows a longitudinal central section of another drier having two dif ferent cages arranged in series in the drum, said section being taken on the line 33 in Fig. 4. Fig. 4 is a cross-section on the line 4-4 in Fig. 3.

Referring now to Figs. 1 and 2 in the drawing, I is the mantle of the drum which is rotatably journalled on rollers 2. At the inlet end the drum is provided with a stationary chamber 3 having a supply chute 4 for the moist goods to be treated and an outlet 5 for the escaping drying gas. At the outlet end of the drum a stationary chamber 6 is provided, said chamber having an outlet 1 for the dried goods and an inlet 8 for the hot drying gas. In Figs. 1 and 2 the drum is shown as having an inset body or cage C having radial partitions. The cage is rigidly secured to the drum so that the drum and the cage rotate as a whole in the operation of the drier.

Fig. 2 illustrates the design of the cage C according to the first embodiment. In this embodi ment the radial partitions l0, II are connected to a central core [2 which, preferably, is hollow. The alternate partitions It, II have different radial lengths in such manner that the partitions I I) extend to the inner wall of the drum while the partitions ll terminate at some distance from said wall. The interior of the drum is divided by the partitions it) into a corresponding number of longitudinal sector shaped channels, each being by a partition I I divided into two sectors A and B having communication with each other at the mantle of the drum. During the operation of this embodiment the material supplied to the drum is caught by the partitions l0 when the drum rotates in the direction indicated by the arrow in Fig. 2 whereupon the material during the rotation of the drum performs a. revolving motion chiefly in the sectors A as indicated by arrows in some of said sectors. In this manner at least one side of the partitions l and l I will always be out of contact with the material so that it can be directly heated by the drying gas and take up heat for a rapid drying of the boundary layer or any goods possible adhering to the opposite side and thus bringing such goods to loosen.

In the embodiment shown in Figs-3 and 4, the rotary drum i is as in the preceding embodiment provided at one end with a stationary chamber 3 having an inlet chute l for the moist goods to be treated and an outlet 5 for the drying gas, and at the other end with a stationary chamber 6 having an outlet 1 for the dried material and an inlet 8 for hot drying gas. In the drum 1 two cages D and are arranged in series. The cage D nearest to the gas inlet end of the drum is firmly secured to: the drum and in well-known manner composed of a central core 12 and of longitudinal, radial partitions l3 all extending from the core to the inner wall of the mantle and dividing the interior of the drum into longitudinal, sector-shaped channels. The other cage E is loosely mounted in the drum so that it can rotate or roll within the drum when the latter rotates, while suitable guiding means (not shown) in the drum prevent it from moving axially. The cage E is, preferably, composed of a central hollow core 42, from which radial partitions Ito. and Ha extend, the partitions a having a greater radial length than the partitions 5 la, the radial length of the partitions 10a, however, being less than the difference between the radii of the drum and the core so that the cage will obtain a somewhat eccentric position in the drum when resting against the lower portion of the mantle with two of its partitions Illa as shown in Fig. 4.. The partitions Mia and Ila divide the interior of the drum in longitu dinal substantially sector-shaped channels A and B which have connection with each other at the periphery of the drum. In the operation of the drum the partitions lta catch the material supplied which then moves forward chiefly through the channels A while performing a revolving movement and is dried by the drying gases flowing through the drum. As in the preceding embodiment at least one side of the partitions will be free from the material so that the partitions can take up heat directly from the drying gas to effect a rapid drying of any goods adhering to the partitions and thus bringing the latter to loosen. The cage E is caused to rotate together with the drum by its friction against the inner surface of the mantle or by means of suitable tappets (not shown) and performs a slow stepwise rotation relatively to the drum in which the outer ends of the partitions Illa impact against the inner mantle surface whereby any material adhering to the partitions of the cage or to the inner surface of the mantle is loosened.

The provision of two different cages as shown in Fig. 3 is not essential to the invention in as much as the cage D can be dispensed with and the loose cage can extend substantially along the whole length of the drum.

Evidently the constructional details in carrying out the invention may be varied without departing from the scope of the invention. In all embodiments a part of the drying gas can be allowed to pass through the central core l2 for facilitating the loosening of goods possibly adhering to its outer surface by heating the core from its inner side. Furthermore, shelves may be provided in well-known manner between the radial partitions for increasing the heating surface.

In the application of the invention to rotary kilns for burning cement or lime a cage accord- .ing to the invention is provided in the inlet end of the kiln tube. The sector system is in this case, preferably, made of fire-proof sheet metal or other refractory material.

What I claimis:

1. 'An apparatus for the treating of pulverulent goods with hot gases, comprising a substan tially cylindrical rotatable drum and a freely rotatable cage having an eccentric position in said drum and consisting of a central core and longitudinal, substantially radial partitions of different lengths forming channels for passing the pulverulent goods and the hot gases in direct contact with each other.

2. An apparatus for the treating of pulverulent goods with hot bases, comprising a substantially cylindrical drum, rotatable in a predetermined direction and a cage in said drum, freely rotatable in relation to the drum, said cage being comprised of longitudinal, substantially radial partitions of alternately different lengths forming channels for passing the pulverulent goods and the hot gases in direct contact with each other, and wall elements extending from the inner end of each long partition to the inner end of the next short partition in front of said long partition in the direction of rotation and closing the space between said two partitions towards the center.

3. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a drum rotatable in a predetermined direction, a cage mounted in said drum and including substantially radial partitions. or" alternately different lengths in the radial direction, dividing the interior of the drum into longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, the space between each long partition and the next short partition in the direction of rotation being closed towards the center and constituting a pocket for said material, which, in rotation allows a rolling movement of said ma terial within the said pocket but prevents said material from passing into the interior of the space between said short partition and the next long partition.

4. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a drum rotatable in a predetermined direction, a cage mounted in said drum and including substantially radial partitions of alternately different lengths in the radial direction, dividing the interior of the drum into longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, the space between each long partition and the next short partition in the direction of rotation being closed towards the center and constituting a pocket for said material, which, in rotation allows a rolling movement of said material within the said pocket, said short partition being of a radial length so as to substantially prevent the material within the pocket from passing over the edge of said short partion.

ent lengths in the radial direction, each long partition extending from the core to the drum and each short partition extending from the core over a substantial radial length, said partitions connecting to the core and dividing the interior of the drum into longitudinal channels for the, passage of the material to be dried and Olf a drying gas in direct contact with each other, each long partition and the next short partition in the direction of rotation together with the intermediate section of the core forming a pock et for said material, which, in rotation allows a rolling movement of said material within the said a length so as to substantially prevent the material within the pocket from passing over the edge of said short partition while performing the upper half of the revolution.

GUSTAV BOJNER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,061,762 Lierfeld May 13, 1913 1,221,412 Bernhard Apr. 3, 1917 1,322,380 Christie 1 Mar. 2, 1920 1,531,780 Greaves Mar. 31, 1925 1,979,602 Bojner Nov. 6, 1934 FOREIGN PATENTS Number Country Date 201,966 Great Britain Aug. 3, 1923 441,326 Great Britain Jan. 17, 1936 pocket, said short partition being of a radial 20 

